System for controlling variable geometry equipment for a turbine engine, especially by bellcranks

ABSTRACT

A system for controlling at least two sets of variable geometry equipment of a turbine engine. The turbine engine includes at least one first body and a second body, the first set of equipment being a stage of variable stator vanes of a compressor of the first body moving between a closed position during idling and an open position at high speed, and the second set of equipment being at least one bleed valve of a compressor of the second body moving between an open position during idling and a closed position at high speed. The actuator drives the second set of equipment by an actuating part that is actuated over part of the course of the actuator and idle on an abutment over the rest of the course, and by a sliding joining element providing a backlash in the actuation of the second set of equipment.

The present invention relates to the general field of the control ofvariable geometry equipment items of a turbine engine. The inventionrelates more particularly to the optimization of the control of severalequipment items forming part of distinct bodies of the turbine engine.

The expression “variable geometry equipment” should be understood hereto mean an equipment item linked to a control member and the dimension,the shape, the position and/or the speed of which is or are likely to bemodified according to detected events or defined parameters, to act onthe operation of the turbine engine. Examples of variable geometryequipment items include air discharge valves of the compressor (withvariable opening), fixed compressor vanes with variable angle, turbinevanes with variable clearance at the tip, variable flow rate fuel pumps,etc.

The term “body” conventionally designates the sub-assembly of a turbineengine, comprising as main members a compressor and a turbine assembledon one and the same axis. Typically a turbine engine may comprise a highpressure body and a low pressure body. Each body comprises a compressorand a turbine, the vanes of which are driven in rotation about the axisof the shaft on which they are mounted.

In general, the various bodies of a turbine engine are designed tooperate independently of one another. Their speed of rotations areindependent, even if they may be linked or correlated in certainoperating speeds.

Therefore, usually, because of this independence between the variousbodies of a turbine engine, to control variable geometry equipment itemsforming part of different bodies, distinct control systems are providedfor these distinct equipment items. For this reason, controlling twovariable geometry equipment items of two distinct bodies generallyrequires two control circuits, two actuators, two power sources, etc. Itfollows that the weight, the cost and the bulk of such a control systemfor the equipment items are relatively high. Such a configuration is theone retained in the applicant's European patent application, publishedunder the number EP 1 724 474.

For example, the low pressure stage may comprise one or more airdischarge valves (often designated VBVs, standing for “variable bleedvalve”), whereas the high pressure stage may comprise one or morevariable angle stator vane stages (often designated VSVs, standing for“variable stator vanes”). To reduce the weight of such equipment itemsand their control members, it is possible to envisage not installing anyVBVs. While the saving achieved in this way is significant (because ofthis, the actuators, the servovalves, the ducting, the harnesses, etc.that are associated with them are eliminated), the risks induced aresignificant, notably at idling speed if water or hail penetrates intothe engine, leading to an increased risk of extinguishing of the latter.

The patent application FR 2 445 439 from General Electric Companydescribes a single means for controlling air discharge valves of a lowpressure stage and variable angle stator stages of a high pressurestage, but this means controls both equipment items essentiallysequentially, only the stator vanes being actuated in normal operationof the turbine engine (that is to say, above idling speed).

The invention aims to propose a turbine engine with variable geometryequipment items belonging to different bodies of the turbine engine anda control system for these equipment items that is optimized.

Thus, the invention relates to a system for controlling at least twovariable geometry equipment items of a turbine engine, the turbineengine comprising at least one first body running at a first speed and asecond body running at a second speed, the first equipment item being avariable angle stator vane stage of a compressor of the first bodymoving between a closed position when idling and an open position athigh speed, the second equipment item being at least one discharge valveof a compressor of the second body moving between an open position whenidling and a closed position at high speed, characterized in that itincludes an actuator which actuates both equipment items.

By using a single actuator to control several (at least two) variablegeometry equipment items, the control system makes it possible to reducethe number of parts of the turbine engine and thus achieve the objectiveof the invention. The weight, the volume and the cost of a secondcontrol system are at least largely avoided since the equipment items ofthe first and second bodies are actuated by the same actuator.

According to one embodiment, the control system is able to control morethan two variable geometry equipment items using a single actuator.

According to one embodiment, a variable geometry equipment item iscommon to several bodies of the turbine engine.

According to one embodiment, the first body being driven at acontrollable speed of rotation, the actuator is controlled by the speedof rotation of the first body.

Thus the equipment item of the second body is controlled by the speed ofrotation of the first body, via the actuator.

According to a particular embodiment, the first body is a high pressurebody and the second body a low pressure body.

In particular, the turbine engine comprising a low pressure compressorand a high pressure compressor, the variable geometry equipment item ofthe low pressure compressor is controlled by the speed of rotation ofthe high pressure compressor.

According to one embodiment, in the case of a turbine engine with a highpressure body and a low pressure body, the variable geometry equipmentitems of the high pressure body are located close to the low pressurebody (for example close to the upstream side of the high pressure body).

According to a particular embodiment in this case, the turbine engine isa dual-body turbine engine with a high pressure body and a low pressurebody. Preferably, in this case, the variable angle stator vane stage orstages forms or form part of the high pressure body, the first equipmentitem controlled by the control system forming part of the low pressurebody of the turbine engine.

According to a particular embodiment in this case, the vane stagecomprises a plurality of vanes, each mounted to pivot on a casing of theturbine engine, and a control ring surrounding the casing is linked toeach of the vanes of the stage via levers, the actuator being able todrive in rotation the control ring of the stage via a driving membermounted on the casing.

According to one embodiment, a variable geometry equipment item is anair discharge valve of the turbine engine. This equipment item maycomprise one valve or a plurality of air discharge valves. It is, forexample, an air discharge valve of the VBV type on the low pressurecompressor.

The control system of the invention can be adapted to control varioustypes of equipment items. In addition to those presented hereinabove,the variable geometry equipment items may notably comprise or form anelement of one or more of the following devices:

-   -   an air discharge valve of the high pressure compressor with        proportional opening (often designated “transient bleed valve”        (TBV) or “start bleed valve” (SBV));    -   an on or off air discharge valve of the high pressure compressor        (often designated “handling bleed valve” (HBV));    -   an airflow rate regulation valve contributing to the clearance        control in a low pressure turbine (often designated “low        pressure turbine active clearance control” (LPTACC)), or in a        high pressure turbine (often designated “high pressure turbine        active clearance control” (HPTACC)).

According to one embodiment, in the control system, the actuatorcomprises a mobile control member, the displacements of which transmitthe control to the variable geometry equipment items. The control membermay, for example, comprise the arm of a cylinder.

According to one embodiment, the actuator is arranged to actuate thefirst variable geometry equipment item by varying a parameter within anactuation band of the first equipment item, the actuator being arrangedto actuate the second variable geometry equipment item by varying thesame parameter within an actuation band of the second equipment item.

The parameter of the actuator indicated hereinabove may, for example, bethe position of the actuation member of the actuator. Thus, thisparameter may be the position of the end of the arm of a cylinder. Thus,in this case, varying this parameter means displacing the end of the armof the cylinder or the position of the working end of the actuator.

According to one embodiment, the actuator drives a return membercomprising at least two branches and mounted to move on the casing ofthe turbine engine, a first branch driving the first equipment item anda second branch driving the second equipment item.

According to a particular embodiment, the second branch drives inrotation, over part of its travel, an actuation part for the secondequipment item and does not drive it over the remainder of its travel,said part remaining at rest on an end stop.

According to a particular embodiment, the actuation part is a lever thatmoves about a rotation axis linked to the casing, a first arm of thelever being intended to cooperate with said second branch and with saidend stop and the second arm driving the second equipment item via asliding junction member forming a dead travel in the actuation of saidsecond equipment item.

When the actuation parameter varies within a range located outside theactuation band of an equipment item, the latter is not actuated by theactuator. Such a range of values of the parameter of the actuator, inwhich no action is actually applied to the equipment item concerned,constitutes a “dead travel” for said equipment item. In such a band,regardless of the variations of the parameter, the actuator does not act(or does not significantly act) on the equipment item concerned.

According to a particular embodiment, the sliding junction membercomprises a first control member having an oblong hole in which slides arod supported by a second control member.

According to a particular embodiment, the rotation axis of the lever canbe displaced along the first arm of said lever.

According to a particular embodiment, the first control member isreturned by an elastic means toward the position corresponding to theabsence of cooperation between the second branch and the actuation part.

According to a particular embodiment, at least a part of the actuationband of the first equipment item is outside the actuation band of thesecond equipment item.

The control of two variable geometry equipment items by a singleactuator may be facilitated by the fact that the actuation bands of thetwo equipment items do not totally correspond, enabling only a singleequipment item to be actuated outside the common region.

According to a particular embodiment, the actuation band of one of thefirst and second equipment items is entirely contained within theactuation band of the other equipment item.

In this case, the equipment items are actuated simultaneously withintheir common region, which may present advantages depending on thenature of the equipment items. Such an embodiment may make it possibleto provide a greater actuation amplitude.

According to a particular embodiment in this case, the actuation band ofone of the equipment items has an amplitude of very much less than theoverall amplitude of the actuation band of the other equipment item; forexample, it may represent less than 20% or less than 10% of this band.In this way, when the band of the equipment item with the reducedactuation band is included within the band of the other equipment item,the control actions of the equipment item lead to only a small and/orinsensitive variation of the control of the other equipment item. Thisarrangement facilitates the control, with a single control system, oftwo equipment items.

The control system is preferably arranged for the variations of theparameter of the actuator between the limits of its actuation band to besufficient to actuate the equipment with sufficient amplitude.

According to one embodiment, the link between the actuator and one ofthe equipment items includes a declutching device, able to declutch thedriving of this equipment item by the actuator over a band of values ofthe actuation parameter. This band of values is therefore situatedoutside the actuation band of the equipment item concerned. Thus, thedeclutching device makes it possible to reserve a range of the actuationband solely for the control of the other equipment item or items. Thismay be essential when the equipment item concerned must not be affected,even when the control of one of the other controlled equipment itemsvaries.

According to one embodiment, the control system also includes returnmeans for maintaining a control member of one of the equipment items ina predetermined position, at least when the parameter of the actuatorvaries within a range located outside the actuation band of theequipment item.

The invention also relates to a turbine engine equipped with a controlsystem described hereinabove.

The invention will be better understood from the following descriptionof the preferred embodiment of the turbine engine and of the inventivesystem, with reference to the appended drawing plates in which:

FIG. 1 represents a perspective view of a system for controlling theposition of variable angle stator vanes according to the prior art;

FIG. 2 is a diagrammatic view of a device for controlling the positionof the discharge valves of a compressor based on the position control ofthe vanes of a variable angle stator according to one embodiment of theinvention; it represents this device in the position that corresponds toa high speed of rotation of the engine (stator vanes open and dischargevalves closed);

FIG. 3 is a diagrammatic view of the same device at intermediate enginespeed of rotation, the stator vanes being in the process of closing andthe discharge valves still being closed;

FIG. 4 is a diagrammatic view of the same device at low engine speed ofrotation, the stator vanes being closed and the discharge valves open;

FIGS. 5 and 6 are curves giving the position of the stator vanes and ofthe discharge valves according to the speed of the engine, in the caseof an overlap and in the case of an absence of overlap in the openingand closure bands of the two equipment items.

As is known, a turbine engine, here of axis X-X, comprises, fromupstream to downstream, a fan, a low pressure compressor (oftendesignated “booster” by those skilled in the art), a high pressurecompressor, a combustion chamber, a high pressure turbine, a lowpressure turbine and a nozzle for ejecting gases (not represented). Thecompressor and the high pressure turbine are fixed to one and the sameshaft, called high pressure shaft, and thus belong to the high pressurebody of the turbine engine, whereas the compressor and the low pressureturbine are fixed to one and the same shaft, called low pressure shaft,and thus belong to the high pressure body of the turbine engine.

Hereinbelow, the following abbreviations will be used:

BP for low pressure and HP for high pressure.

The HP compressor comprises at least one stage formed by a wheel ofmobile vanes and a wheel of fixed vanes (also called stator vanes). Eachstage is formed by a plurality of vanes positioned radially around theX-X axis of the turbine engine. In the case in point, the HP compressorcomprises a plurality of stages, with alternating wheels of mobile vanesand wheels of fixed vanes. The vanes are enclosed in a cylindricalcasing which is centered on the axis X-X of the turbine engine.

Among the fixed vane wheels, at least one stage 10 comprises vanes 14said to be of variable angle. Each vane 14 is mounted to pivot about anaxis 16 (or pivot) which passes through the casing 12. The angularposition of each vane 14 can be adjusted by driving the pivot 16 thereofin rotation.

The stage 10 of variable angle vanes forms a first variable geometryequipment item, belonging to the HP body (since it belongs to the HPcompressor). The variable parameter of this equipment item is the angleof the vanes 14; in the case in point, all the vanes 14 are drivensimultaneously in rotation, by virtue of a ring 22 controlling the stage10 of vanes 14.

The control ring 22 is of overall circular shape; it surrounds thecasing 12 and is centered on the axis X-X of the turbine engine. Thesynchronized modification of the angular position of the vanes 14 isthus obtained by a rotation of the control ring 22 about the axis X-X ofthe turbine engine, as is known.

The turbine engine comprises a second variable geometry equipment item110. In the case in point, it is an air discharge valve, of the VBV type(represented diagrammatically herein). The variable parameter of thisequipment item 110 is the opening angle of the discharge valve 110. Thisequipment item 110 belongs to the BP body of the turbine engine. Thefunction of the VBV valve 110 is to discharge air at the outlet of theBP compressor to reduce the risks of poor operation of this compressorwhen it is operating in particular conditions.

Obviously, as is known, the second equipment item 110 could include aplurality of such valves.

The control system is arranged to control the rotation of the controlring 22 of the stage 10 of variable angle vanes (first equipment item10), and the displacement of a control member 115 for the secondequipment item 110.

To this end, the control system comprises an actuator 24, in the case inpoint a cylinder 24, which is mechanically linked to the first equipmentitem 10 and to the second equipment item 110 to drive them in movement.A single actuator 24 thus controls two variable geometry equipment items10, 110 of two distinct bodies.

To this end, each pivot 16 of the variable angle vanes 14 is linked toone end of a controlling connecting rod 18 or lever 18, the other end ofwhich is articulated around a trunnion 19 fixed to the control ring 22and extending radially relative to it.

The ring comprises at least one end fitting 27 to which is fixed one endof a control rod 32, of the stretching screw type, extending roughlytangentially to the ring 22. The other end of the control rod 32 isfirmly attached to a so-called driving (because it is directly linked tothe actuator 24) return member 26, mounted to pivot on a module 28 ofthe casing 12 of the turbine engine. The driving return member 26 ismore specifically T-shaped. The control rod 32 is fixed to one end of afirst branch 34 of the T, the end of the rod of the cylinder 24 beingfixed, in an articulated manner, to the end of the actuation branch 42of the T which is located in the extension of the first branch 34. Thesecond branch 38, perpendicular to the other two, fulfills anotherfunction, described below. The driving return member 26 is mounted topivot about an axis 50 extending at the intersection of the branches.

The actuator (cylinder) 24 can drive in rotation the control ring 22 ofthe variable angle vane stage 10 via the driving return member 26, whichtransmits the movement of the cylinder 24 to the control rod 32 which inturn transmits the movement to the ring 22 to which it is firmlyattached in translation (curvilinear).

The driving return member 26 and the rod 32 are the main elements of themovement transmission chain from the actuator (cylinder 24) to thecontrol ring 22.

The cylinder 24 is controlled by an electronic control unit. Itsmovements depend on the speed of rotation N2 of the HP compressor.

The invention has been presented with a single variable angle vane stagebut obviously it can be implemented with a plurality of stages, thestages being linked conventionally with a first return 26, calleddriving return, and returns 26′, called following returns, driven via asynchronization bar 30.

The control system also controls the displacement of a control member115 for the second equipment item 110, using a specific device.

Now referring to FIGS. 2 to 4, a device 60 for actuating dischargevalves using the control system for the variable angle stator vanes canbe seen. The return member 26, which is mobile in rotation about theaxis 50, generates the displacement of the rod 32 via its first branch34, and that of a synchronization bar 30 via its second branch 38; italso drives an actuation part 65 via its branch 38. This actuation part65 is in the form of an L-shaped lever, and is mobile in rotation abouta first axis 51 linked to the casing 12. It is permanently returned byan elastic return means, not represented, toward the second branch 38and rests, in the absence of cooperation with the branch 38, on an endstop 64. One of its arms is able to cooperate with the second branch 38to transmit the rotation of the return member 26 to a U-shaped stirrup126 which is attached to the second arm of the part 65, by a secondarticulation 52. A rotation of the return member 26 is reflected in alongitudinal displacement of the stirrup 126 which is displaced like atype of rod being displaced in a slideway.

The two branches of the stirrup 126 pass either side of a first controlmember 115 of the variable geometry 110, which controls thedisplacements of the variable geometry equipment item 110 in thedirection indicated by the arrow A. This control member 115 is in theform of a rectangular plate with an oblong hole 124. The two branches ofthe stirrup 126, forming a second member for the control of the secondequipment item 110, are linked by a rod 122 which passes through theoblong hole 124, in which it slides.

The stirrup 126 and the rod 122 constitute the sliding junction member120. The actuator 24 drives the second equipment item 110 via thissliding junction member 120, the sliding of which defines a dead travelD. In practice, as long as the rod 122 is displaced inside the elongatehole 124 without being locked at one end of the latter, this will causeno movement of the control member 115, in other words the movements ofthe actuator (the cylinder 24) do not cause any movement of the controlmember 115 of the equipment item 110.

In the absence of action on the part of the return member 26 on theactuation part 65, a spring 112 pushes back the control member 115 andmaintains the second equipment item 110 in the position corresponding tothe closed position of the discharge valves. The return spring of thepart 65 causes the latter to be rotated about the second articulation 52until it comes against the end stop 64 which limits the rotation of theactuation part in the direction of closure of the stator vanes. It isthen held bearing against the end stop 64 by the elastic return meansmentioned above.

Finally, the actuation part 65 is, as represented in FIGS. 2 to 4, inthe shape of an L, the two arms of which join at the first rotation axis51. The length of its first arm, that is to say, the arm whichcooperates with the branch 38 of the return 26, can be reduced bydisplacing the point where it is fixed to the rotation axis. Thisdisplacement causes the gearing of the movement that exists between therotation of the return 26 and the displacement of the stirrup 126 to bemodified. The amplitude of this gearing modification is determined bythe travel B along which the rotation axis 51 can be displaced.

Referring to FIGS. 5 and 6, the relative opening laws of the variableangle vanes (referenced VSV) and of the discharge valves (referencedVBV) can be seen as a function of the speed of rotation N2 of the HPbody. The greater the value of the curve, the more open thecorresponding variable geometry equipment item 10, 110 becomes. The openposition of the vanes VSV 14 corresponds to the position in which theyallow the greatest flow of air to pass into the HP compressor 3; theopen position of the valves VBV 110 corresponds to the position in whichthey take the maximum air flow rate from the BP compressor.

In a first phase P1, at low speed, the discharge valves VBV 110 are openwhile the variable angle vanes VSV 14 are closed. In a second phase P2,at intermediate speed, the valves VBV 110 are gradually closed as thespeed N2 of the HP body increases, whereas the vanes VSV 14 aregradually opened as the speed N2 of the HP body increases; at the end ofthe second phase P2, the valves VBV 110 are almost completely closedwhereas the vanes VSV 14 are around two thirds open. In a third phaseP3, the closure of the valves VBV 110 is finalized whereas the openingof the vanes VSV 14 is gradually finalized as the speed N2 of the HPbody increases.

Thus, the two variable geometry equipment items 10, 110 are driven bythe speed of the HP body. In particular, the valves VBV 110, belongingto the BP body, are controlled by the speed of rotation N2 of the HPbody. The result of this is a simplification of the definition of theopening laws and a guarantee of good synchronization between theopenings and closures of the variable geometry equipment items sincethese openings and closures depend on one and the same single parameter:the speed of rotation N2 of the HP body.

In the version V1 represented in FIG. 5, the opening of the variableangle vanes VSV begins at the same time as the closure of the dischargevalves VBV, but ends after, whereas in the version V2, represented byFIG. 6, it begins only after their closure. The choice of one version,and the exact moment at which the closure of the discharge valvesbegins, are defined by acting on the position and the length D of theoblong hole 124. An elongation or a shortening of this opening shiftsthe opening of the discharge valves, in one direction or the other,relative to the closure of the variable angle vanes.

As indicated previously, a modification of the positioning of the firstrotation axis 51 on the first arm of the actuation part 65, within thelimit of the travel B, results in a modification of the gearing of themovement generated by the rotation of the return 26. A shortening of thearm of the L increases the rotation of the actuation part 65 for a givenrotation of the return 26, which is reflected in a faster opening of thedischarge valves and a tangent at the point of inflection of the VBVcurve in FIG. 6 that is more vertical. Conversely, an enlarging of thelever arm on the first arm of the actuation part 65 will produce atangent at the point of inflection of the curve in FIG. 6 that is lessvertical and a more gradual opening of the discharge valves.

In order to convey an understanding of how the control system 1operates, FIGS. 2 to 4 illustrate the movement of this system in threepositions, corresponding to a maximum, intermediate and minimumextension of the cylinder 24. In the control system 1, the extension ofthe cylinder 24 is the actuation parameter of this actuator.

There now follows a description of the operation of the stator vanes andof the discharge valves during a modification of the speed of rotationN2 of the HP body, taking for example a deceleration of the engine fromthe full throttle position. In this initial situation (FIG. 2) thecylinder is in the maximum extension position; the variable angle vanes14 are in the open position and the discharge valves are closed. Thebranch 38 of the return member 26 is distant from the first arm of theactuation part 65 which rests against the end stop 64, under the actionof the elastic return means of the part 65. The spring 112 maintains thecontrol member 115 in the position corresponding to the discharge valvesbeing closed.

From this position, the actuation of the cylinder 24 provokes a rotationof the driving return 26, and, where appropriate, that of a followingreturn 26′ driven by the synchronization bar 30. The rotation of thereturn 26 about its pivoting point on the module 28 in turn drives therod 32 which then rotates the ring 22 in one direction or the otherabout the axis X-X of the turbine engine. As indicated previously, therotation of the ring 22 causes a synchronized modification of theangular position of the vanes 14 of the stage 10 via control levers 18.

With the speed of rotation decreasing, the return 26 revolves until themoment when its second branch 38 comes into contact with the first armof the actuation part 65, as illustrated in FIG. 3 which corresponds toa specific position during the contraction of the cylinder 24.

With the cylinder 24 contracting further, the return 26 begins to rotatethe actuation part 65 about its rotation axis 51 and consequently pushthe rod 122 of the stirrup 126 in the oblong hole 124, in the directionof the arrow A. The position represented in FIG. 3 is specific in thatit corresponds to the precise moment when the rod 122 firmly attached tothe stirrup 126 comes to a stop at the end of the hole 124 in thedirection of the arrow A (which is the direction of actuation for thecontrol member 115), a position from which the rod 122 begins to drivethe control member (plate 115) of the variable geometry 110. Conversely,from the beginning of the contraction of the cylinder 24, and as far asthis position, the control member 115 is not displaced from its initialposition (FIG. 2) despite the displacement of the stirrup 126.Therefore, the actuation band of the cylinder 24, between its initialposition (FIG. 2) and the specific intermediate position of FIG. 3,constitutes a dead travel D for the second controlled equipment item110. During this movement, the valves of the stator are gradually closedwhereas the discharge valves remain fully closed.

On the other hand, from the start of actuation position that appears inFIG. 3, any additional contraction of the cylinder 24 causes the rod 122firmly attached to the stirrup 126 to push back, in the direction of thearrow A, the control member 115 and causes a displacement of the latter.The positions of the cylinder 24 that are contracted further than inthis position constitute the actuation band of the second equipment item110. The discharge valves consequently open. This opening occurs more orless gradually depending on the adjustment B retained for the length ofthe lever arm of the actuation part 65.

It should be noted in addition that, when the cylinder 24 exceeds thisstart of actuation position, the spring 112 acts as return means tomaintain the control member 115 in permanent contact with the rod 122.Thus, outside of the dead travel, the control member 115 follows, ateach instant, the displacements of the rod 122, in the direction of thearrow A and in the opposite direction. Conversely, in the dead travel ofthe sliding junction member 120, the control member 115 remainsimmobilized, in the “left-hand” position in FIGS. 2 and 3, under theeffect of the elastic return means of the actuation part 65.

With the speed of rotation continuing to reduce, the cylinder iscontrolled to full retraction, which corresponds to discharge valvescompletely open and a continuing closure of the stator vanes, until theyare fully closed (position illustrated in FIG. 4).

In line with the increase in the speed of rotation N2 from idling speed,the cylinder 24 extends and rotates the return member 26 in the oppositedirection to the preceding direction. Under the action of its elasticreturn means, the actuation part 65 returns to its end stop 64 drivingwith it the stirrup 126. The control member 115, no longer being subjectto the pressure of the rod 122, accompanies, under the action of thespring 112, the stirrup 126 in its displacement which initiates theclosure of the discharge valves. The movement of the control member 115continues until the spring 112 is fully expanded, then the rod 122,still driven by the elastic return means of the actuation part, travelsalong the oblong hole 124 until it abuts against the other end of thishole. The assembly comprising actuation part 65, stirrup 126 and controlmember 115 continues its travel until the first arm of the actuationpart 65 encounters the end stop 64.

In this position, the discharge valves are fully closed. The opening ofthe stator vanes, for its part, continues with the rotation of thereturn 26, the movement of which from this instant no longer interfereswith that of the discharge valves.

Although the invention has been described in relation to severalspecific embodiments, it is obvious that it is in no way limited theretoand that it comprises all the technical equivalents of the meansdescribed and their combinations providing that the latter fall withinthe context of the invention.

1-12. (canceled)
 13. A system for controlling at least first and secondvariable geometry equipment items of a turbine engine, the turbineengine including at least one first body and a second body, the firstequipment item being a variable angle stator vane stage of a compressorof the first body moving between a closed position when idling and anopen position at high speed, the second equipment item being at leastone discharge valve of a compressor of the second body moving between anopen position when idling and a closed position at high speed, thesystem comprising: an actuator driving a return member including atleast two branches and mounted to move on the casing of the turbineengine, a first branch driving the first equipment item and a secondbranch driving the second equipment item, wherein the second branchdrives in rotation, over part of its travel, an actuation part for thesecond equipment item and does not drive the actuation part over aremainder of its travel, the actuation part remaining at rest on an endstop.
 14. The control system as claimed in claim 13, in which the firstbody is a high pressure body and the second body a low pressure body.15. The control system as claimed in claim 13, in which the actuator iscontrolled by a speed of rotation of one of the bodies of the turbineengine.
 16. The control system as claimed in claim 15, in which theactuator is controlled by a speed of rotation of the high pressure body.17. The control system as claimed in claim 16, in which the actuationpart includes a lever that moves about a rotation axis linked to thecasing, a first arm of the lever configured to cooperate with the secondbranch and with the end stop, and the second arm driving the secondequipment item via a sliding junction member forming a dead travel inthe actuation of the second equipment item.
 18. The control system asclaimed in claim 17, in which the sliding junction member includes afirst control member having an oblong hole in which a rod supported by asecond control member slides.
 19. The control system as claimed in claim17, in which the rotation axis of the lever is configured to bedisplaced along the first arm of the lever.
 20. The control system asclaimed in claim 18, in which the first control member is returned by anelastic means toward a position corresponding to absence of cooperationbetween the second branch and the actuation part.
 21. The control systemas claimed in claim 16, in which the actuation band of the secondequipment item is included within the operating band of the firstequipment item.
 22. A turbine engine comprising a control system asclaimed in claim 13.